[user104658]

I reckon it's just to get the US to dip into their extraordinary military budget and give us some of their stuff (because of the UK's strategic importance as a US ally in Europe).

Realistically if it came down to it, the US would supply a UK-at-war with as many planes, drones and missiles as we need. The stock they have and the money they've spent compared to any other country in the world is just staggering. Even if they stopped developing and building new and just maintained what they have, it would take any other global power decades to come anywhere close to catching up.